Subtractive methods for creating dielectric isolation structures within open features

ABSTRACT

A method for partially filling an open feature on a substrate includes receiving a substrate having a layer with at least one open feature formed therein, wherein the open feature penetrates into the layer from an upper surface and includes sidewalls extending to a bottom of the open feature. The open feature is overfilled with an organic coating that covers the upper surface of the layer and extends to the bottom of the open feature. The method further includes removing a portion of the organic coating to expose the upper surface of the layer and recessing the organic coating to a pre-determined depth from the upper surface to create an organic coating plug of pre-determined thickness at the bottom of the open feature, and converting the chemical composition of the organic coating plug to create an inorganic plug.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related and claims priority to U.S. ProvisionalPatent Application Ser. No. 62/146,386 filed on Apr. 12, 2015, theentire contents of which are herein incorporated by reference.

FIELD OF INVENTION

The invention relates to methods for partially filling an open featureon a substrate, and in particular, to methods for forming a dielectricplug at the bottom of the open feature in a semiconductor device.

DESCRIPTION OF RELATED ART

The need to remain competitive in cost and performance in the productionof semiconductor devices elevates demand to continually increase thedevice density of integrated circuits. And, to achieve higher degrees ofintegration with the miniaturization in semiconductor integratedcircuitry, robust methodologies are required to reduce the scale of thecircuit pattern formed on the semiconductor substrate. These trends andrequirements impose ever-increasing challenges on the ability to prepareelectrical structure isolation during circuit pattern fabrication.

Photolithography is a mainstay technique used to manufacturesemiconductor integrated circuitry by transferring geometric shapes andpatterns on a mask to the surface of a semiconductor wafer. Inprinciple, a light sensitive material is exposed to patterned light toalter its solubility in a developing solution. Once imaged anddeveloped, the portion of the light sensitive material that is solublein the developing chemistry is removed, and the circuit pattern remains.Furthermore, to advance optical lithography, as well as accommodate thedeficiencies thereof, continual strides are being made to establishalternative patterning strategies to equip the semiconductormanufacturing industry for sub-30 nm technology nodes.

One type of circuit pattern includes trenches etched into a substrate,e.g., a silicon substrate, such that a plurality of fins composed of thesubstrate material extend from the bottom of the trenches.Traditionally, these trenches were filled with a dielectric material,through various methods, to minimize the undesirable transfer of currentbetween adjacent fins. This transfer of current occurs through processessuch as leakage. The dielectric material was meant to insulate the spacebetween adjacent fins, thus decreasing the flow of electrons and holestherebetween. The fins were typically of uniform height.

When adding the dielectric material, various methods were used to ensurethat the dielectric material filled the trenches to the top of adjacentfins and maintained a relatively planar surface over the face of thesemiconductor chip. In each method, however, the dielectric material wasdirectly applied to the surface. A plurality of metal gates could thenbe placed over the surface so that a conducting channel was formed inthe silicon region, i.e., the top of the fin, when in the “on” state.

However, as the size of integrated circuits became smaller, the planarengagement of the metal gate with the silicon region led tounsatisfactory performance of the chip. In response to thisunsatisfactory performance, three-dimensional transistors weredeveloped, in which the dielectric material did not extend to the top ofthe trench, thereby exposing three surfaces of the silicon fin. A metalgate was then placed over the fin, making contact with all three exposedsurfaces, so that conducting channels formed on all three sides of thefin.

Nonetheless, partially filling an open feature, such as the trenchesdescribed above, with a typical dielectric material, such as an oxidematerial, is difficult. Therefore, there is a need for methods forselectively filing only a portion of an open feature of a semiconductordevice with a dielectric material.

SUMMARY OF THE INVENTION

Embodiments of the invention relate to a method for partially filling anopen feature on a substrate, and in particular, a method for forming adielectric plug at the bottom of the open feature.

According to one embodiment, a method for partially filling an openfeature on a substrate includes receiving a substrate having a layerwith at least one open feature formed therein, wherein the open featurepenetrates into the layer from an upper surface and includes sidewallsextending to a bottom of the open feature. The open feature isoverfilled with an organic coating that covers the upper surface of thelayer and extends to the bottom of the open feature. The method furtherincludes removing a portion of the organic coating to expose the uppersurface of the layer and recessing the organic coating to apre-determined depth from the upper surface to create an organic coatingplug of pre-determined thickness at the bottom of the open feature, andconverting the chemical composition of the organic coating plug tocreate an inorganic plug.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 provides a schematic representation of an open feature withinwhich a material is to be formed to partially fill the open feature;

FIGS. 2A-2E illustrate an exemplary method according to an embodiment;

FIGS. 3A-3E illustrate an exemplary method according to anotherembodiment;

FIG. 4 provides exemplary data obtained in accordance with oneembodiment; and

FIGS. 5A-5D illustrate an exemplary method according to anotherembodiment.

FIGS. 6A-6G illustrate an exemplary method according to yet anotherembodiment.

DETAILED DESCRIPTION OF SEVERAL EMBODIMENTS

In the following description, for purposes of explanation and notlimitation, specific details are set forth, such as a particular processflow for a processing system or collection of systems. However, itshould be understood that the invention may be practiced in otherembodiments that depart from these specific details.

Similarly, for purposes of explanation, specific numbers, materials, andconfigurations are set forth in order to provide a thoroughunderstanding of the invention. Nevertheless, the invention may bepracticed without these specific details. Furthermore, it is understoodthat the various embodiments shown in the figures are illustrativerepresentations and are not necessarily drawn to scale.

Various operations will be described as multiple discrete operations inturn, in a manner that is most helpful in understanding the invention.However, the order of description should not be construed as to implythat these operations are necessarily order dependent. In particular,these operations need not be performed in the order of presentation,unless stated otherwise. Operations described may be performed in adifferent order than the described embodiment. Various additionaloperations may be performed, and/or described operations may be omittedin additional embodiments.

“Substrate” as used herein generically refers to the object beingprocessed in accordance with the invention. The substrate may includeany material portion or structure of a device, particularly asemiconductor or other electronics device, and may, for example, be abase substrate structure, such as a semiconductor wafer or a layer on oroverlying a base substrate structure, such as a thin film. The substratemay be a conventional silicon substrate or other bulk substratecomprising a layer of semi-conductive material. As used herein, the term“bulk substrate” includes not only silicon wafers, but alsosilicon-on-insulator (“SOI”) substrates, such as silicon-on-sapphire(“SOS”) substrates and silicon-on-glass (“SOG”) substrates, epitaxiallayers of silicon on a base semiconductor foundation, and othersemiconductor or optoelectronic materials, such as silicon-germanium,germanium, gallium arsenide, gallium nitride, and indium phosphide. Thesubstrate may be doped or undoped. Thus, the substrate is not intendedto be limited to any particular base structure, underlying layer oroverlying layer, patterned or un-patterned, but rather, is contemplatedto include any such layer or base structure, and any combination oflayers and/or base structures. The description below may referenceparticular types of substrates, but this is for illustrative purposesonly and not limitation.

As noted above, advanced methodologies are required to partially fill anopen feature, such as a trench or via/hole, with a dielectric material.The dielectric can fill the bottom of the trench or via/hole, and can beformed to contact the sidewalls imposed by the confining structure, forexample, up to at least the top of the dielectric itself. The dielectricmaterial can be selected to be thermally resistant, and meet apre-determined electrical requirement, e.g., provide electricalisolation of one electrical structure relative to another. Furthermore,among other things, the methods described herein can reduce or minimizedamage to the open feature and surrounding structure by the inclusion ofthe dielectric material.

Therefore, according to various embodiments, a subtractive method isdescribed based on filling the open feature with an organic material,which is capable of filling features of relatively small criticaldimension (CD) and/or high aspect ratio without voids or substantiallywithout voids, removing a portion of the organic material from the openfeature, and then converting the remaining organic material into adielectric material through various reactive mechanisms. FIG. 1 is adiagrammatic illustration of a portion of an exemplary semiconductordevice formed by the inventive methodologies. Semiconductor device 10includes substrate 12 and an open feature, particularly a trench 14,formed in a material layer 16 having an upper surface 18. Trench 14 isdefined by sidewalls 20 that are separated by width W and extend to abottom 22 of the trench 14. A dielectric plug 24 is formed at the bottom22 of the trench 14.

Several embodiments describe the process flows that can yield thedesired dielectric structure within an open feature, such as a trench orvia. A brief summary of exemplary process flows are outlined below, andinclude the following: (i) coat (overfill) the feature; (ii) recess thematerial into feature; and (iii) convert to a dielectric material withinthe feature.

Scheme A

-   -   a) Coat with polymeric material containing a carbonyl        functionality    -   b) Expose material to UV light to break chemical bonds    -   c) Rinse away decomposed organic material with solvent    -   d) Incorporate aluminum atoms into matrix    -   e) Remove remaining organic material and create aluminum oxide        dielectric        Scheme B    -   a) Coat with a polymeric material containing low acidic —OH        functionality    -   b) Rinse away a portion of the organic material with standard        developer    -   c) Silylate —OH functionality    -   d) Remove remaining organic material and oxidize silicon to make        SiO₂ dielectric        Scheme C    -   a) Coat with spin-on-carbon film    -   b) Use UV ozone process to etch back polymer    -   c) Infiltrate with source of metallic atoms        Scheme D    -   a) Coat trenched semiconductor with photoactive film    -   b) Flood exposure where wavelength of light prevents penetration        into the trenches    -   c) Over-coat with acid-containing film    -   d) Diffusion bake to drive acid into material    -   e) Develop with a timed develop step

Several embodiments describe methods for forming a dielectric plug atthe bottom of a trench, as shown in FIG. 1. The materials thatconstitute the bottom of the trench may be the same or different in eachembodiment, and the dielectric material forming the plug may be meant tofill only a small part of the trench. As noted earlier, this dielectricmaterial may electrically isolate two electrically active structures,while being capable of withstanding a considerable thermal profile. Asthis dielectric material is formed, the process flow may be selected tominimize damage to the sidewalls or bottom of the existing structure.

In several embodiments, a track system can be used to perform thesubtractive methods described herein. Track systems, including coaterand developer systems, include modules capable of spin coating materialsonto a substrate, thermally treating materials on the substrate, andchemically treating the materials on the substrate. Track systems arecommercially available from Tokyo Electron Limited. One technique tocreate a dielectric plug is to fill the open feature with a spin-ondielectric, and then, using an etch back process, either wet or dry, thedielectric material can be recessed into the feature. However, thisprocess is difficult in practice.

Therefore, in accordance with embodiments described herein, the processsequences include over-filling the trenches with an organic material,etching back to recess the material within the open feature, and thenconverting the organic material into a dielectric material.

Turning now to the figures, FIGS. 2A-2E provide a schematic diagram ofan exemplary process in accordance with an embodiment. As shown in FIG.2A, an organic coating 26 is deposited on the substrate 12 in such a waythat trench 14 is overfilled. A polymer such as poly(methylmethacrylate) (PMMA), for example, may be used for the organic material.PMMA as the organic coating 26 exhibits favorable gap-fillingcharacteristics, and thus, can be used to fill open features with asmall width W and/or high aspect ratio such that the PMMA fully extendsto the bottom 22 of the trench 14 and covers the upper surface 18.Further, PMMA can be formulated with a wide range of molecular weight,and at reduced molecular weight, gap-filling performance improves.

After the organic coating 26 is formed, it is exposed to electromagneticradiation 28 such as ultraviolet (UV) light, as shown in FIG. 2B, tomodify a portion of the organic coating 26, including the portion thatcovers the upper surface 18 and extending to a pre-determined depth inthe trench 14 to form a modified portion 30. When low molecular weight(or oligomeric) PMMA is used for organic coating 26, for example, UVexposure may be desirable. UV light can break the bonds of the PMMAbackbone, making the modified portion 30 a decomposition product that issoluble in organic solvents.

Depending on the size of the open features, and the wavelength of lightused, the optical properties of the organic coating 26 may be matched tothe optical properties of the surrounding structure of material layer16, such as the trench or via sidewall 20, so that low wavelength oflight can penetrate the structure. For example, UV light with awavelength ranging from approximately 170 nm to approximately 180 nm,such as 172 nm light, can be used to effectively penetrate openings ofwidth W that are quarter wavelength (43 nm) or greater. However, if theoptical properties of the organic coating 26 are made to match theoptical properties of the surrounding structure of material layer 16through addition of a small amount (i.e., low concentration) of a dye,then the coated structure will appear to the exposing wavelength to be amore optically homogeneous material and penetrate deeper into the openfeatures. Thus, the addition of an appropriate dye may be used to tailorthe depth of penetration of the light and, as a result, the height ofthe dielectric plug 24 (FIG. 1) within the open feature of thesemiconductor device 10.

Once the exposure has occurred, the organic coating 26 is recessed intothe trench 14 through wet development with an organic solvent such as analcohol or organic acid, to remove the modified portion 30, as shown inFIG. 2C. In certain embodiments, isopropyl alcohol (IPA) or acetic acidcan be used. In the same or different embodiments, developers commonlyassociated with positive tone resists may be used. Alternatively,developers commonly associated with negative tone resists may also beused. The etch rate of the modified portion 30 can depend on the amountof UV exposure used. Also, the amount of UV exposure can control themolecular weight of the PMMA polymer remaining in the open feature,i.e., the unmodified portion of organic coating 26 at the bottom 22 oftrench 14. Therefore, the molecular weight and amount of the unmodifiedportion of the organic coating 26 remaining may be controlled bytailoring the etch rate and carefully monitoring the time of UVexposure.

Following the etch-back of the organic coating 26, the remainingmaterial is converted into an inorganic material, in particular adielectric to form dielectric plug 24, as shown in FIG. 2D. PMMA, forexample, is known to undergo aluminum sequential infiltration synthesis(SIS) through the carbonyl group in the methacrylate moiety, thusallowing aluminum atoms to be incorporated into the organic material.The SIS process is self-propagating, i.e., subsequent cycles of the SISprocessing lead to subsequent incorporation of aluminum into the film.Following the SIS step, the organic material can be removed, and thealuminum can be converted to a viable aluminum oxide dielectric materialas dielectric plug 24.

Conversion can be accomplished through a number of known oxidationmechanisms. In one example, oxidation can be performed by thermallybaking at high temperature to “burn” the organic. In another example,oxidation can be performed by creating in-situ ozone as an oxidizingagent. In another example, oxidation can be performed by utilizing a wetoxidation treatment, such as aqueous ozone or a peroxide mixture, e.g.,hydrogen peroxide. A mixture of deionized water, aqueous ammoniumhydroxide, and hydrogen peroxide, e.g., an SC-1 solution, can be used.In yet another example, oxidation can be performed using a plasma etchtreatment, in which oxygen is used to oxidize the organics in the filmwhile converting the aluminum to aluminum oxide. The plasma of thismechanism does not require oxygen as a constituent in the plasma-forminggas because PMMA contains atomic oxygen. Plasma systems capable ofgenerating high density plasma with low damage, e.g., reduced energy,electron temperature, or bias power, can reduce damage to the substrateduring oxidation.

Following the oxidation in FIG. 2D, heat 32 can be applied in a hightemperature bake process to remove any residual organic material, asshown in FIG. 2E.

The process flow is described above with reference to PMMA as theorganic coating 26, but the invention is not so limited. In fact, thereare many possible materials that can be chosen in place of PMMA.However, the material should possess at least one of the followingtraits: (i) solubility in an appropriate solvent for spin-coating oralternative coat mechanisms, such as inkjet; (ii) favorable gap-fillingcharacteristics; (iii) removability through wet or dry means; and (iv)presence of a carbonyl functionality so that aluminum SIS can beachieved.

In alternative embodiments, a silylation mechanism may be used toconvert the organic material into a dielectric material, as will bedescribed below in reference to FIGS. 3A-3E.

This sequence is similar to that above shown with the SIS process, buthas some important differences. One representation of this approach iswith a poly(hydroxystyrene) (PHOST) polymer as the organic coatingmaterial. This polymer contains a phenolic moiety that is readilysilylatable. These polymers have also been used as BARC (bottomanti-reflective coatings), and possess favorable coating and gap fillingproperties as well. Following depositing an organic coating 26′ of thePHOST material on the substrate 12, as shown in FIG. 3A, the PHOSTmaterial is readily etched back through the use of a standard developingsolution, as shown in FIG. 3B. The developing solution can contain, forinstance, tetramethylammonium hydroxide (TMAH), tetrabutylammoniumhydroxide (TBAH), methyl isobutyl carbinol (MIBC), 2-heptanone, n-butylacetate, isopropyl alcohol, anisole, propylene glycol monomethyl etheracetate (PGMEA), ethyl lactate, methyl amyl ketone, gamma-butyrolactone,propylene glycol monomethyl ether (PGME), methyl isobutyl ketone (MIBK),cyclohexanone, or combinations of two or more thereof. Such materialscan be used when removing at least a portion of the organic materialused to fill the open features, i.e., trench 14.

The wet developer may allow the PHOST material of organic coating 26′ tobe recessed within the trench 14. However, PHOST has a high developmentrate in standard developer, so it can be difficult to control such aprocess. One technique to provide greater control is to use a dilutedeveloper ( 1/10^(th) the concentration of standard developer) so thatthe material develops at a more manageable rate. Another approach wouldbe to use a co-polymer that consists of PHOST and a protected-PHOST,which is poly(hydroxystyrene) with protecting groups attached to thependant phenolic groups. Protecting groups can includetertbutoxycarbonyloxy (TBOC) or tetrahydropyran (THP), for example. Thedevelopment of these copolymers in a developer, such as TMAH developer,can be controlled by the copolymer ratio of the various co-monomers,wherein the development rate slows as the proportion of PHOST in thecopolymer lowers. Additionally, novolac polymers, i.e.,phenol-formaldehyde resins, could also be used in place of PHOST. Thesepolymers have the same chemical functionality, but have branched chainsrather than linear chains, and can have lower development rates in suchdevelopers. Copolymers of PHOST and t-butyl acrylate (ESCAP), forexample, may also be used to coat the substrate, and again, thedevelopment rate can be controlled by varying the copolymer ratio withthe development rate slowing as the proportion of PHOST in the copolymerlowers. Such copolymers include regions that can undergo silylation,i.e., the PHOST portion, and SIS, i.e., the t-butyl acrylate portion.Other copolymers may be used for development rate control that includeone polymer with functional groups that readily undergo silylation,while the other polymer contains carbonyl functional groups that undergoSIS, Further alternative materials that can be used as organic coating26′ include hydroxyl naphthyl polymers, which include hydroxyl groupsbound to aromatic naphthyl groups and are expected to react similarly tothe phenol groups of PHOST.

Once the PHOST material of the organic coating 26′ has been recessedwithin the open feature, e.g., trench 14, the remaining PHOST materialmay be silylated with any of a number of silylating agents to give plug34, as shown in FIG. 3C. Silylating agents may be secondary or tertiaryamines that contain silicon in the groups attached to the amine. Forexample, possible silylating agents may include hexamethyldisilazane(HMDS), trimethylsilyldimethylamine (TMSDMA), dimethylsilyldimethylamine(DMSDMA), dimethyldisilyldimethylamine (DMDSDMA), and mixtures thereof.These agents may be administered in the gas phase. Alternatively, theseagents can be administered in a liquid phase, e.g., agents used in theCARL Process (Chemical Amplification of Resist Lines). An exemplaryliquid silylating agent is bisaminopropyl-oligodimethylsiloxane.

The phenolic group in the PHOST material of the organic coating 26′ hasa suitable chemical reactivity for silylation in reasonable times atrelatively low temperatures. This phenolic group is of moderate acidityfor an organic functionality (pK_(a)=9). Aliphatic alcohols can besilylated (pK_(a)=12), but can take a long time to do so, and carboxylicacids are more resistant to readily undergo silylation because theirincreased acidity (pK_(a)=5) forces the silylation reaction equilibriumto lie to the side of the unsilylated state. Accordingly, those skilledin the art will recognize that the pK_(a) of the component that willundergo silylation in the filling material may vary. An exemplary rangeof the pK_(a) is from about 7-10. Additionally, alcohols that have twotrifluoro groups attached to the same carbon are readily silylatable atlow temperatures and times because they have a pK_(a) similar to phenol.

In the example given above, each phenolic site can undergo silylation,thereby incorporating a silicon atom at each phenolic site. Therefore,assuming complete silylation of a film, the number of silicon atoms thatare incorporated into the film is equal to the number of phenolic sitesin the film multiplied by the number of silicon atoms in the functionalgroup attached to the amine. In subsequent steps, the atomic silicon maybe used for converting the film to a silicon dioxide. Thus, it may bedesirable to incorporate a large amount of silicon into the film. If100% PHOST is used, each monomer unit has a phenolic site that can besilylated. If a copolymer containing protecting groups is used insteadof pure PHOST, however, the protected co-monomer may requiredeprotection, which can be achieved thermally at temperatures above thethermal stability of the protecting group in question. Alternatively, athermal acid generator (TAG) can be placed into the film to generateacid under the application of heat, and this acid can, in turn, removethe protecting group. Furthermore, another method for deprotecting thepolymer would be to incorporate a photo-acid generator (PAG) into thematerial, expose the PAG to an appropriate wavelength of light, and bakethe semiconductor device 10 to remove the protecting group.

If a copolymer of PHOST and t-butyl acrylate, for example, is used asthe organic coating 26′, a sequence of silylation and SIS, in eitherorder, may be performed to give plug 34 with silicon atoms incorporatedthrough silylation and aluminum atoms incorporated through SIS. Morebroadly speaking, if the copolymer contains a functionality having apK_(a) of about 7 to about 10 capable of undergoing silylation (but notSIS) and a carbonyl functionality capable of undergoing SIS (but notsilylation), then both silicon atoms and aluminum atoms can beincorporated by performing silylation and performing SIS either beforeor after the silylation. If either co-monomer (or both) includesprotecting groups, the co-monomer may be deprotected, as discussedabove, prior to silylation and SIS, to remove the protecting groups.

Once the silylation is complete, the incorporated silicon can beoxidized to create a silicon dioxide dielectric material as thedielectric plug 24 at the bottom 22 of the trench 14 as shown in FIG. 3Dand heat 32 can be applied to remove any residual organic material, asshown in FIG. 3E. This can be accomplished through similar mechanisms asdescribed above for the aluminum conversion. In one embodiment, theplasma treatment is especially advantageous. If both silicon andaluminum atoms are incorporated through a combination of silylation andSIS, then both are oxidized to create a silicon dioxide and aluminumoxide dielectric plug 24.

Another subtractive method involves the use of a spin-on-carbon (SOC)film, a type of amorphous carbon. SOC films possess favorable gap-fillproperties and can be used to planarize topography.

FIG. 4 provides results for a UV-assisted etch back process on asubstrate overfilled with an SOC. UV light at 172 nm in an ambientatmosphere is used to create ozone. The ozone can etch back the SOC filmin fairly uniform fashion. FIG. 4 shows the impact of the UV exposuretime. As shown in FIG. 4, the UV ozone process uniformly etches back theSOC film in a non-destructive fashion. Initially, the coating is 145 nmthick in and over trenches that are 100 nm deep. After 80 seconds ofUV-etching, the coating is 99 nm thick and essentially fills thetrenches to the top of the fins. After 120 seconds of UV-etching, thecoating is 66 nm thick and now falls below the top edge of the fins.Finally, after 180 seconds of UV-etching, the coating is 35 nm thick andlines only the bottom of the trenches.

As shown in FIGS. 5A-5D, the overall process flow is similar to theprocess illustrated in FIGS. 2A-2E and 3A-3E, but the material that isapplied in FIG. 5A as the organic coating 26″ is the SOC film, and theUV ozone process 36 is used to etch back the film, as shown in FIG. 5B.To convert the SOC film of organic coating 26″, a liquid infiltrationprocess can be used to incorporate titanium atoms into the SOC film togive plug 38, as shown in FIG. 5C. This incorporation can be followed byoxidation of the titanium using one or more of a high thermal treatment,a dry ozone oxidation, a wet ozone oxidation, a wet process usingammonium hydroxide and peroxide, or a plasma process involving oxygenspecies to create a titanium oxide dielectric material as the dielectricplug 24, as shown in FIG. 5D. These oxidation methods are known and willnot be discussed further.

Yet another subtractive method for creating the plug is shown in FIGS.6A-6G. In this embodiment, a photoactive film is used as the organiccoating 26″ to overfill the open features, e.g., trenches 14, as shownin FIG. 6A. In this example, a duty cycle of 3:1 is shown, but theinvention is not so limited. An appropriate photoactive film will beboth alterable by electromagnetic radiation and alterable upon contactwith an acid rinse, as will be discussed further below. For instance,the photoactive film may include phenolic or acrylic moieties, amongothers.

After overfilling with organic coating 26″, and as shown in FIG. 6B, aflood exposure with electromagnetic radiation 28′, e.g., UV radiation,is performed with a wavelength of light that is greater than 4 times thewidth W of the trenches (i.e., the quarter wavelength is greater thanthe width W). Light of wavelength A cannot penetrate openings with widthW that is less than ¼ of λ. Accordingly, when a properly sized trench orpattern of trenches are filled or overfilled with a photoactivematerial, the portion of the photoactive materials within the trench maynot be chemically altered by the exposure of light, e.g., may not berendered dissolvable in the given wet developing chemistry. However, thephotoactive material outside or over the trench may be chemicallyaltered as a result of the light exposure, e.g., may be rendereddissolvable in the given wet developing chemistry. In this way, aportion of the photoactive material may be selectively altered, suchthat the altered and unaltered portions may respond in different ways tosubsequent processing. Therefore, the light sensitive photoactivematerial in the trenches 14 may not be impacted, or have a reducedimpact, when the semiconductor device 10′ is exposed to electromagneticradiation 28′. Thus, the photoacid that is in the unaltered portion ofthe photoactive material within the trenches 14 is not exposed to theflood exposure shown in FIG. 6B, and so the material within the trenches14 remains non-acidic after the exposure. In other words, the unalteredportion of the photoactive material inside the trenches 14 (i.e., thefill portion) may retain the properties of an unexposed photoactivematerial, while the altered portion of the photoactive material outsideof the trenches 14 (i.e., the overfill portion) may have the propertiesof an exposed photoactive material. As shown in FIG. 6C, a wetdevelopment process may then be performed to remove the altered overfillportion of the organic coating 26′″ that was exposed to the floodexposure. The organic coating 26′″ remaining in the trenches 14 and theupper surface 18 of material layer 16 form a planarized surface.

Next, as shown in FIG. 6D, semiconductor device 10′ is coated with acidrinse 40. Alternatively, although not shown, a feeder film containingacid (akin to a topcoat with acid) could be coated on top of thestructure. If this feeder film is used, then the feeder film can beselected to be soluble in the solvent that will complete the developmentof the photoactive material in the last step of the process.

After the acid rinse, a timed diffusion bake is performed to give adeprotected film 42, as shown in FIG. 6E. The bake drives the acid downinto the film and causes deprotection of the photoactive material. Asnoted above, the photoacid that was in the trench 14 originally was notexposed, and so it is still non-acidic at this point in the process.Thus, the depth of deprotection within the trench is controlled by thelength of time and/or the temperature of the diffusion bake. As the timeperiod gets longer and/or the temperature increases, more acid canpenetrate within the film. For example, an exemplary temperature for thediffusion bake is 70-200° C. The penetration can also be controlled bythe amount of acid deposited during the acid rinse step. Thus, thepenetration may be controlled by the acid concentration in the rinseitself.

Thereafter, a timed develop step enables the removal of the deprotectedfilm 42 to a set depth, as shown in FIG. 6F, leaving a small amount ofthe photoactive material of organic coating 26′″ at the bottom 22 of thetrench 14. As shown in FIG. 6G, an infiltration method can be performedthereafter to introduce a desired atomic species to convert theremaining organic coating 26′″ to a dielectric material for thedielectric plug 24. The atomic species may in part depend on the natureof the photoactive film that was originally coated.

Following this process sequence eliminates potential issues that mayarise from non-uniformity of the photoactive film as the organic coating26′″. Considering an array that consists of trenches 14 of the same sizeas those shown in FIG. 6A, but on a 5:1 duty cycle (not shown), thephotoactive film will overfill these trenches more than the densertrenches 14 shown in FIG. 6A. The flood exposure, then, allows the filmheights across the different trench densities to be equalized orplanarized. The trenches 14 act to filter the light so that adequateexposure can be used to remove the excess film from the less dense arrayof trenches without impacting the more dense trenches. When theoverfilled portion of the photoactive film of organic coating 26′″ isremoved, as shown in FIG. 6C, the photoactive film may be discontinuousthroughout the material layer 16. Further, the upper surface 18 and thephotoactive film may form a continuous surface, as depicted in FIG. 6C.

In one example, the photoactive film used for organic coating 26′″ canbe a copolymer of t-butyl acrylate and methylmethacrylate formulatedwith 3% triphenylsulfonium nonaflate photoacid generator. The t-butylgroup on the acrylate co-monomer is acid labile. After coating and floodexposure, the t-butyl group in the overfill portion will be deprotectedor cleaved, and the film can be developed in standard TMAH developer.Next, an acid rinse 40 consisting of nonaflatic acid in appropriatesolvent is applied to the material. The film is baked to diffuse theacid into the trench where additional deprotection occurs to the desireddepth, and the deprotected film 42 within the trench can then be removedwith developer. The timed diffusion bake controls the depth ofpenetration of the acid and the subsequent height of material remaining,i.e., a t-butyl acrylate/methylmethacrylate plug.

Following the creation of this t-butyl acrylate/methylmethacrylate plug,the remaining t-butyl groups are thermally cleaved in a deprotectionbake (not shown). Thus, both co-monomers of the block copolymer mayundergo aluminum SIS. After infiltration, the oxidation methodsdescribed above may be used to create an aluminum oxide plug as thedielectric plug 24.

Although only certain embodiments of this invention have been describedin detail above, those skilled in the art will readily appreciate thatmany modifications are possible in the embodiments without materiallydeparting from the novel teachings and advantages of this invention. Forinstance, the concepts contained herein apply not only to trenches insemiconductor devices but also to vias/holes. Accordingly, all suchmodifications are intended to be included within the scope of thisinvention.

The invention claimed is:
 1. A method for partially filling an openfeature on a substrate, comprising: receiving a substrate having a layerwith at least one open feature formed therein, the open featurepenetrating into the layer from an upper surface and including sidewallsextending to a bottom of the open feature; over-filling the open featurewith an organic coating that covers the upper surface of the layer andextends to the bottom of the open feature; removing a portion of theorganic coating to expose the upper surface of the layer and recessingthe organic coating to a pre-determined depth from the upper surface tocreate an organic coating plug of pre-determined thickness at the bottomof the open feature; and converting the chemical composition of theorganic coating plug to create an inorganic plug, wherein the organiccoating includes a polymeric material or co-polymeric materialcontaining a carbonyl functionality, and wherein removing the portion ofthe organic coating includes performing a wet etch process comprising:exposing the organic coating to ultraviolet (UV) radiation to increasethe solubility of the as-formed organic coating in a developingsolution; and controllably etching the organic coating to thepre-determined depth by exposing the organic coating to the developingsolution.
 2. The method of claim 1, wherein converting the chemicalcomposition of the organic coating plug includes performing a metalinfiltration synthesis process and then performing an oxidation process.3. The method of claim 1, wherein converting the chemical composition ofthe organic coating plug includes exposing the organic coating plug totrimethylaluminum (TMA) and then an oxygen environment to create aninorganic plug composed of an aluminum oxide dielectric material.
 4. Themethod of claim 1, wherein the UV radiation exposure is conducted at aUV wavelength ranging from approximately 170 nm to approximately 180 nm.5. The method of claim 1, wherein the UV radiation exposure is conductedat a UV wavelength having a quarter wavelength less than or equal to anopening dimension of the open feature, measured as the distance betweenthe sidewalls of the open feature.
 6. The method of claim 1, wherein theorganic coating contains a dye of a concentration selected to increasethe penetration of the UV radiation into the open feature.
 7. The methodof claim 1, wherein the developing solution contains tetramethylammoniumhydroxide (TMAH), tetrabutylammonium hydroxide (TBAH), methyl isobutylcarbinol (MIBC), 2-heptanone, n-butyl acetate, isopropyl alcohol,anisole, propylene glycol monomethyl ether acetate (PGMEA), ethyllactate, methyl amyl ketone, gamma butyrolactone, propylene glycolmonomethyl ether (PGME), methyl isobutyl ketone (MIBK), orcyclohexanone, or combinations of two or more thereof.
 8. The method ofclaim 1, wherein the polymeric material further includes a functionalityhaving a pKa of about 7 to about
 10. 9. The method of claim 8, whereinthe polymeric material includes poly(hydroxystyrene) (PHOST) andoptionally a protected PHOST.
 10. The method of claim 9, wherein theprotected PHOST contains a protecting group selected from the groupconsisting of tert-butoxycarbonyl (TBOC) or tetrahydropyran (THP). 11.The method of claim 10, wherein converting the chemical composition ofthe organic coating plug includes deprotecting the organic coating plug,performing a silylation process, performing an oxidation process, andremoving residual carbon from the inorganic plug.
 12. The method ofclaim 11, wherein performing the silylation process includes exposingthe organic coating plug to a silylating agent selected from the groupconsisting of hexamethyldisilazane (HMDS), trimethyl silyldimethylamine(TMSDMA), dimethylsilyldimethylamine (DMSDMA),dimethyldisilyldimethylamine (DMDSDMA), andbisaminopropyl-oligodimethylsiloxane.
 13. The method of claim 8,wherein, converting the chemical composition of the organic coating plugincludes performing a silylation process and a metal infiltrationsynthesis process in either order, performing an oxidation process, andremoving residual carbon from the inorganic plug.
 14. The method ofclaim 13, wherein the polymeric material is a copolymer ofpoly(hydroxystyrene) (PHOST) and t-butyl acrylate.
 15. A method forpartially filling an open feature on a substrate, comprising: receivinga substrate having a layer with at least one open feature formedtherein, the open feature penetrating into the layer from an uppersurface and including sidewalls extending to a bottom of the openfeature; over-filling the open feature with an organic coating thatcovers the upper surface of the layer and extends to the bottom of theopen feature; removing a portion of the organic coating to expose theupper surface of the layer and recessing the organic coating to apre-determined depth from the upper surface to create an organic coatingplug of pre-determined thickness at the bottom of the open feature; andconverting the chemical composition of the organic coating plug tocreate an inorganic plug, wherein the organic coating includes aphoto-active material, and wherein removing the portion of the organiccoating includes planarizing the organic coating with the upper surfaceof the layer, de-protecting the organic coating to the pre-determineddepth within the open feature, and removing the de-protected organiccoating.
 16. The method of claim 15, wherein planarizing the organiccoating includes: exposing the organic coating to ultraviolet (UV)radiation; and thereafter, exposing the organic coating to a developingsolution to remove the exposed portion of the organic coating, the UVradiation exposure being a flood exposure conducted at a UV wavelengthhaving a quarter wavelength greater than an opening dimension of theopen feature, measured as the distance between the sidewalls of the openfeature.
 17. The method of claim 15, wherein de-protecting the organiccoating to the pre-determined depth includes: exposing the organiccoating to an acid solution; and diffusing acid through the organiccoating to the pre-determined depth of the organic coating in the openfeature.